I have:
 
Braid
Spelunky
VVVVVV
Machinarium
Half-Life (this is an indie game, yeah?)

I own Gish, Alien Hominid, Braid, Aquaria, Minecraft, World of Goo, VVVVVV, Bit.Trip Beat, and uh... the Half-Life series.
My decision to by those games had nothing to do with Super Meat Boy. The only two I bought after the game came out were Bit.Trip Beat and Minecraft, but them being in SMB was irrelevant. I knew about Commander Video being in the game, but that didn't influence my decision to buy the game. And Steve wasn't announced yet when I bought Minecraft.

I have Minecraft but I'm not sure the dude is in SMB (wow I just got that) yet.

I already had a couple of Bit Trip games, Half Life, World of Goo, Minecraft, and Braid.

Actually yes, I downloaded Allmighty Jill, N+, VVVVVV, I Wanna Be The Guy, Spelunky, Knytt and that other game from the Knytt maker. And I bought an indie pack on steam with Gish in it.
I barely played them, but I did it just this week because I got a laptop with a bad graphics chip and I thought a few indie games would be nice.

Most of them, but the only one I finished was I Wanna Be The Guy.

It's Super Meat Boy's fault I'm now hooked on Jumper.

No. Though I already owned Alien Hominid, Gish, N+ and Castle Crashers before playing Super Meat Boy.
 
Heck, I even played a lot of Jumper (2) what must have been like 5 or 6 years ago, back when Matt Thorson was still known as YoMamasMama.

I owned or had played most of them already.

I downloaded Jumper, and RunMan because of SMB, but already owned Machinarium, World of Goo, and I Wanna Be The Guy.. and Half Life of course. 

I played VVVVVV, World of Goo, Half Life and I Wanna Be The Guy before I heard of Super Meat Boy. However I hadn't heard of a few of the other characters and I am interested in trying their games out.

I have both Alien Hominid and Half-life 1, 2 and the episodes.

I have WoG, HL (no duh) and Braid...but I already had those.
 
EDIT: Oh yeah, I have Alien Hominid on the PS2.

I've played Half Life and own Castle Crashers. That is it, though.

It has come to my attention that I bought Machinarium during Steam's Black Friday sale, which was partially motivated by Super Meat Boy. My previous vote for B does not take into account this oversight.

I've been playing Gish forever. That's an oldie.

None actually because of SMB.  I've owned Braid and Aquaria for a while (and all the Half-Life games, of course), and I've played the demos for Gish, World of Goo, Machinarium, and VVVVVV.  Oh, and I played Alien Hominid's flash game on Newgrounds a long time ago.

Wait, Tim from Braid and the World of Goo goobers are in Super Meat Boy? If so, then I must change my answer.

B.
 
Got Alien Hominid, Castle Crashers, and Braid before I even heard of this game.

"Wait, Tim from Braid and the World of Goo goobers are in Super Meat Boy? If so, then I must change my answer. "

I already had Gish, Braid, Machinarium and bit.trip BEAT along with HL2 (but I'm not sure if you'd consider Valve an indie developer).

I played about half of those games prior to even hearing about the meatboy.

Already a big VVVVV, Braid and Castle Crashers fan before SMB but SMB did make me check out Flywrench.  I guess I also have any other games that were in either humble bundle but I haven't played much of those.

All said, though, I can't be the only one who felt like Twisted Pixel got left hanging in the wind a bit. Kind of an off omission. Though maybe they opted out.